This grant is designed to develop, validate and clinically apply a new noninvasive method, computed cardiac tomography (CCT), for defining the locale and quantifying the volume of ischemic and/or infarcted myocardium following coronary occlusion. These assessments will be made in experimental animals and clinical subjects under varying circumstances and at varying times after ischemic insult to the myocardium. A CCT unit gated to specific events in the heart cycle will be used to measure attenuation coefficients in normal, ischemic and infarcted myocardium. Contrast agents will be employed both to delineate the cavity-myocardial wall interface (thus noninvasively providing information equivalent to ventriculography) and to identify the margins of ischemic or infarcted zones in the myocardium. CCT determinations will be related to electrocardiographic, enzyme and radionuclide indicators of myocardial ischemia and infarction during life as well as to the gross and histologic appearance of the heart in vitro. The reproducibility and precision of detecting and sizing ischemic and infarcted myocardium will be determined by comparing in vivo data with postmortem examination. A series of interventions designed to increase or reduce the size of the ischemic and infarcted zones will be used to assess the sensitivity and specificity of CCT measurements.